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TT: Tiefe Temperaturen

TT 3: Schwere Fermionen

TT 3.1: Vortrag

Montag, 26. März 2001, 09:30–09:45, A

Pseudogap in the optical spectra of UPd₂Al₃ — •M Dressel¹, B Gorshunov¹, N Kasper¹, K Petukhov¹, D Peligrad¹, M Huth², and H Adrian² — ¹Physikalisches Institut, Uni-Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart — ²Institut für Physik, Uni-Mainz, Staudinger Weg 7, 55099 Mainz

The optical properties of thin film of heavy fermion (HF) compound UPd₂Al₃ were studied at frequencies 10 GHz up to 1.2 THz in the ranges of temperature 2 K <T< 300 K and of magnetic field up to 8 T. At T<25 K a well pronounced pseudogap with E_g ≈ 0.22 meV develops in the optical response; this feature does not arise from the gap in magnetic excitation spectra. We also found a narrow conductivity peak centered at zero frequency which is less than 1 cm⁻¹ wide and which contains only a fraction of the delocalized carriers. Our findings may be a consequence of the hybridizaton gap inherent in HF; for UPd₂Al₃ the value is strongly reduced compared to the Kondo coupling energy due to low concentration of screening electrons (exhausting regime).